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If in DeltaABC, a=2b and A=3B, then A is...

If in `DeltaABC`, a=2b and A=3B, then A is equal to

A

`90^(@)`

B

`60^(@)`

C

`30^(@)`

D

None of these

Text Solution

Verified by Experts

The correct Answer is:
A
`because a=2b`
`thereforesinA=2sinB`
`thereforesin3B=2sinB`
`therefore3sinB-4sin^(3)B=2sinB`
`sinBne0`
`therefore4sin^(2)B=1`
`thereforesinB=(1)/(2)`
`thereforeB=30^(@)`
`thereforeA=3B=90^(@)`
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